While I'm still in the process of meeting my neighbors (I've been here less than a month) I've unfortunately already had to deal with the issue of excessive noise from next door, one of the most common new neighbor dilemmas faced after moving in. To help reduce distractions while working from home, and more importantly, also during sleep hours, I've been following several recommendations for combating "neighbor noise"...

Talk to Your Neighbors. This should be the first action taken, because sometimes people are just not aware of how loud they've become, and once informed, most people will quiet down. Just be realistic about noise expectations and present yourself in a friendly manner, as this past thread illustrates your "loud neighbor" might be a victim of the inherent acoustics of the building itself.

Insulate Your Home. Since this post is directed at apartment dwellers, when I say "insulate", I'm not talking about the pink-stuff for inside the walls. Instead, I'm thinking about insulating the walls with art on walls, tapestries, curtains, rugs, all of these lovely decor things can help you to create a sound barrier between apartments. Vahan had an informative post about how to reduce echoes inside a room using decorative elements to reduce acoustic bounce which may help tune down the ambient noises both from within and coming into your apartment.

Bring on the White Noise. White noise from fans, white noise machines, air filters, air conditioners, are all effective at various degrees for helping to mask annoying sounds. This won't work for the very loudest of neighbors, but white noise can definitely ease intruding noises. The most recommended white noise machine on Amazon is the $52 "so ugly, it has to be good" Dohm-DS Dual Speed Sound Conditioner by Marpac.

Noise Cancelling Headphones. If loud noises are particularly bothersome during day hours, try wearing some noise-cancelling headphones. I have a pair of Bose QC 15s, and since they work wonders while flying, I'm hoping they'll also do the trick the next time the neighbors get loud.

Soft Earplugs. For more serious sleep-time noise intrusions, I personally recommend Mack's Pillow Soft Earplugs. I have very tiny ears and have found Mack's split in half fit fine and really do help blocking out a considerable percentage of loud ambient sounds.